When I first saw "the ick" it was used to capture a really specific and subtle feeling - the moment when, seemingly out of nowhere, something innocuous about a person's behaviour was suddenly and inexplicably off-putting to you. You knew the feeling was irrational and the behaviour innocuous so it wasn't a judgment, but it struck a chord because it was so often a signal that something deeper in the relationship wasn't right.
It's now been overused and misused to the point where I want to scratch my own eyes out whenever I see it. Most of the time when I see it now, people are just using it as a vehicle for their own unexamined and deeply stupid prejudices and hang-ups (often class-based, often about traditional gender signifiers), but because it's "the ick" they can never be challenged or have to reflect on why they find a man in a cheap shirt or a man with long hair so viscerally repellent. And it's done with all the subtlety of a 9-year-old bully in the playground sneering "you smell!"